Transformer Sizing

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wasasparky

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What code section states that a transformer must be sized to our load calculation?

Remember that common sense and good engineering practice are not required by code. (That probably didn't come out right but hopefully you know what I mean...)
 
All I can offer is 110.3(B). That, and you have to protect the transformer against overcurrent, per 240.4.
 
The code contains provisions that a considered necessary for safety however they may not be efficient. Follow 110.3B as Charlie stated and protect the transformer with overcurrent protection per Section 450.3 (240.4 is for protection of conductors)
 
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wasasparky said:
What code section states that a transformer must be sized to our load calculation?

Remember that common sense and good engineering practice are not required by code. (That probably didn't come out right but hopefully you know what I mean...)
Click to expand...

It may be over sized. Your question is not clear. Do you want to install a smaller transformer KVA that the calculated load?
 
bob said:
It may be over sized. Your question is not clear. Do you want to install a smaller transformer KVA that the calculated load?
Click to expand...

The question is quite clear.

I am reacting to a statement in another forum that the transformer "must be sized per code"... when it appears the code does not address what size to use.

The utility is good at sizing their transformer well below what our load calculations indicate. It appears that we could do the same thing on our side of the fence...

I think most dry-types are well underloaded because of this, and I am as guilty as anyone...
 
wasasparky said:
I think most dry-types are well underloaded because of this, and I am as guilty as anyone...
Click to expand...
This is partly the reason the relatively recent Energy Act requires all new 'standard' transformers to be designed to be most energy efficient at 35% loading.
 
So in a nutshell, if someone says a transformer has to be sized per code, we can tell them no, the code does not dictate how to size.
 
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